No side effects from your COVID vaccine? Don't worry, it's still working

(HealthDay)—Even if you don't have side effects from your COVID-19 vaccine, it's likely still working to protect you, a reassuring new report shows.

Many people who receive the mRNA COVID vaccines by Pfizer and Moderna experience body aches and fatigue that indicate the vaccine is triggering their immune system to recognize and fight the coronavirus.

But what if you feel fine and have no such symptoms?

In the new study, researchers looked at 206 hospital employees at Walter Reed National Military Medical Center for antibodies against the coronavirus before and after they received the two-dose Pfizer vaccine.

The employees received their vaccines between December 2020 and January 2021, were followed until March 2021, and had lab work conducted in April and May.

As in clinical trials, the most commonly reported symptom among the study participants was arm pain, with rates of 91% after the first shot and 82% after the second.

After their first shot, 42% of participants reported feeling tired or weak, and 28% reported body aches and pains. After their second shot, 62% reported feeling weak or tired, and 52% reported body aches and pains, the findings showed.

Being female, younger and having a lower weight were associated with increased vaccine side effects.

However, the researchers at the Uniformed Services University of the Health Sciences (USU) found no link between the presence or severity of side effects and a person's level of immune system antibodies one month after vaccination, according to the study published in the January issue of the journal Open Forum Infectious Diseases.

The researchers explained that mRNA-based vaccines teach the body's cells how to make a protein or a piece of protein that triggers an immune response inside the body.

"Our findings suggest people receiving these vaccines can be reassured that lack of post-vaccination symptoms does not mean that the vaccine is not working as intended," study author Si'Ana Coggins, a scientist in USU's department of microbiology and immunology, said in a university news release.

"These results also suggest that it may be possible to design future mRNA vaccines that offer robust antibody responses with fewer vaccine-related symptoms," Coggins added.

The researchers are now investigating whether there's a connection between vaccine side effects and longer-term antibody responses.

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